Method of and means for increasing the capacity of drying installations



'Jan.8,1929. I 1,697,927

' J. G. OLSSON METHOD OF AND MEANS FOR INCREASING THE CAPACITY OF DRYING INSTALLATIONS Filed March 7, 1927 2 Sheets-Sheet 1 Y f 5 56 25 56 lave/afar:

Jofian Gus/a/ 019.900

Jan. 8, 1929., 1,697,927

J. G. OLSSON METHOD OF AND MEANS FOR INCREASING THE CAPACITY OF DRYING INSTALLATIONS Filed March 7, 1927 2 Sheets-Sheet Z @Mmr mn 1 z s 4- 5 s 7- 8 s 4 7 I K g5 25 ZI Wen/or: Johan Gus/0f 012900 Patented Jan. 8, 192 9.

, UNITED STATES PATENT orrlcg J OHAN GUSTAF OLSSON, 0F STOCKHOLM, SWEDEN, ASSIGNOR TO'AKTIEBOLAGET SVEN- SKA FLKKTFABRIKEN, OF STOCKHOLM, SWEDEN, A REGISTERED COMPANY.

METHOD OF AND MEANS FOR INCREASING THE CAPACITY OF DRYING INSTALLATIONS.

Application 'filed- March 7, 1927, Serial No.

The present invention relates to amethod of increasing the capacity of drying installations in which the heat required for the drying is supplied to the drier directly, for instance by means of steam, and also toa means for carrying out this method. The present method is particularly intended to be applied to the dryingof paper and chemical pulp on drying cylinders, that is to say, in the soealled drying sections of paper machines, pulp drying machines, and the like, in which the drying cylinders which are usually heated by means of steam, are placed uncovered in the machine room, but the present method may also be utilized to advantage with other driers in which the drying takes place in a similar manner. In such drying installations, in order to prevent condensation of water in the machine rooms from the hot and moist air escaping from the drier, it is necessary to superheat the vapor in said air. In order that the heat necessary for such superheating shall not require to be taken from the drying cylinders, it has, been proposed to force into the machine room heated fresh air which supplies such large heat quantities that the saturated vapor rising from the drying section becomes superheated so that condensation of water is prevented. When supplying heated fresh air in this manner, however, it might easily happen that the temperature in the machine room becomes too high so that it causes discomfort to the operators to remain in the same. From the point of view of heat economy it would be advantageous if the temperature of the supplied fresh air could be maintained very high, but in view of the circumstancejust mentioned this is not possible; and therefore, it has been necessary instead to supply very large quantities of fresh air heated to a comparatively low temperature, which results in a poorer heat econblow, the purpose of the method forming the subject of the present invention is to avoid these difficulties. The method consists principally in that the heating of the fresh air supplied for the purpose 0 the saturated vapor is efiected in such manner that a portion of the air is heated to a higher temperature than the remaining portion, and that the portion of the fresh air heated to the higher temperature is dissuperheating 173,290, and in Sweden November 29, 1926.

room. In this manner it becomes possible to 1 superheat that portion of the fresh air, which shall effect the superheating of the vapor, to a very high temperature, 100C. or thereabove, and thus to attain a good heat economy, this portion of the fresh air containing such large quantities of heat that the drying cylinders need give off no heat other than that required for evaporating the water from the material. Simultaneously the possibility is reached of regulating the temperature in the room in such manner that it does not cause discomfort to the workmen. For attaining a, further saving of heat it may be suitable to utilize the hot and moist air escaping from the drying installation for heating the fresh air in such manner that the hot and moist air is conducted through at least two heat ex changers for heating freshair arranged in succession, so that in this manner a portion of the fresh air is heated to a higher temperature than the-remaining portion. The portion of the fresh air heated to the higher temperature and which is to effect the superheating of the saturated vapor, may afterwards, after being further heated, if required, for in stance by the aid of condensed water from the drying cylinders, or alternatively, by the use of steam, be let out below the drier and be caused to flow upwards along the sides of the drier, and if desired, also through the drier itself, so that it comes in intimate contact with the hot and moist air escaping from the material.

In such drying installations in which the evaporation of water is different from different portions ofthe drier, as-is the case, for instance, inrespect of the drying sections of paper machines, pulp drying machines, and the like, it may be suitable to regulate the admission of the heated fresh air which is to effect the superheating of the vapor, to i the drier in such manner that the fresh air quantities admitted at various points approximately correspond to the quantities of water evaporated from corresponding portions of .machine is mounted, the section being-taken immediately in front of the drying section of the machine. Fig. 2 shows a slightly modified construction of the means for admitting the heated fresh air below the drying section .of the paper machine. Fig. 3 is a diagram which illustrates the evaporation from different portions of the drying section of the machine, and Fig. 4 illustrates a manner of regulating the admission of the fresh air to correspond to such evaporation.

Referring to the "drawing, 1 denotes the drying cylinders of the paper machine which are assumed to be heated in the ordinary manner by means of steam admitted through the tube 2, the condensed water being discharged through the tube 3. Directly above the drying cylinders 1 there is provided an opening 4 1n the ceiling of the paper machine room through which opening the hot and moist air escaping from the drying section may pass up to two heat exchangers 5 and 6 mounted in the room above the paper machine room. Said heat exchangers may be constructed, in

- a manner previously known, of a plurality of namel parallel plates between which passages are formed in such manner that air may be conducted through the heat exchanger in two directions at right'angles to one another,

in the one direction, viz, the vertical irection, the hot and moist air which is to give off heat, and in the other direction, viz, e horzontal direction, the cool fresh air to be heated. The hotand moist air is drawn through said two heat exchangers-in succession bymeans of a fan 7, after which it is passed out into the open through the duct 8 which extends upwards through the roof. of the building. Below the opening 4 a tra 9 is suspended which serves to col lect t e condensed water dripping from'the heat exchangers 5 and 6, such water flowing ofi through the pipe 10.

Two ducts 11 and 12 project upwards through the roof of the building and form I inlets for the fresh air which is drawn in by means of fans 13 and 14, respectively. The fresh air drawn in by the fan 13 is passed through the upper heat exchan er 6, through which the hot waste air'from t e drying section passes last, in the horizontal direction from left to rightin Fig. 1 and becomes then heated somewhat, for instance to about 20 0 after which it is conducted downwards nected which extend horizontally along the side walls of the machine room, said pipes 18 as well as the pipe 15 being provided with aperatures 19 through which the air is discharged into the machine room. Furthermore, those portions of the pipe 15 which extend through the chambers 17 below the floor 16, may also be providedwith apertures 20v through which a quantity of the air flows out into said chambers from which it flows up into the machine room through openings 21 in the floor 1.6. In this manner an efficient hot Waste air from the drying section passes first, that is to say, while said air is hottest, in a'horizontal direction from right to left in Fig. 1 and is thus more highly heated, for instance to about 40 (1, after which said. air is conducted through the pipe 22 to a passage 23 which extends between the two chambers 17 below all dryingcylinders 1, and into which the air is allowed to pass out through apertures 24 in a number ofpipes 25 located in the longitudinal direction of said passage and connected with the pipe 22. From the passage 23 the air 'flows through openings 26 ina floor27 covering the passage up below the drying cylinders 1, so that it may be caused to flow upwards mainly along the two sides of the drying section, i. e. past the ends of. the drying cylinders, where said air mixes with the moist air which evaporates from the web of material running over the drying cylinders. In order that the fresh air discharged ditional heater 28 in which the air is further heated by means of the condensed water from the drying cylinders 1, or, alternatively, by

the aid of steam.

To the pipe 22 there is further connected a pipe 29 which communicates lat both ends with other pipes 30, which extend'lengthwise closely below the ceiling of themachine room,

and which are provided with fine outflow at all, need be discharged through the pipes 30. Inorder to render possible regulation of those quantities of air which are to be conducted to the pipes 30 and to the passage 23, there are provided adjustable dampers 31 and 32 in the pipes 29 and 22, respectively. Finally, in the pipe 29v there may be inserted heaters 33 in which the air may be further heated, if required, for'instance by means of steam, before it is allowed to escape adjacent the ceiling of the machine room.

The one fresh air admitting duct 12 with associate fan 14 may be omitted if, as indicated in Fig. 1 with dashed lines, the fresh air outlet of the heat exchanger 6 be instead connected with the fresh air inlet of the heat exchanger 5 by means of a pipe 34. In such case the entire fresh air quantity is drawn in through the duct 11, and the fan 13 should therefore be of a correspondingly larger size. In this case there should also be inserted dampers 35 and 36 in the pipes 15 and 34, respectivel by means of which dampers the fresh air quantities admitted to the different places of consumption may be controlled.

The curve shown in Fig; 3 indicates the .tion of the means for admitting the heated evaporation from different portions of the drying section illustrated in Fig. 4 as consisting of nine pairs of drying cylinders. As will be seen from this curve, the evaporation from the web of material 37, which is assumed to run over the drying cylinders in the direction indicated .by the arrows in Fig. 4, varies quite considerably at the different pairsiof drying cylinders, On the first pair of cylinders the evaporation is quite inconsiderable, after which it increases and reaches its maximum on the third cylinder pair, again to decrease all the way to the last cylinder pair. In order to attain the full efiic'iency of all drying cylinders the supply of the strongly heated fresh air from the passage 23 is controlled, according'to the invention, in such manner that the fresh air quantities supplied at the various points approximately correspond to the quantities of water eva aorated from corresponding cylinder pairs. s indicated in Fig. 4, the different openings 26 in the floor 27 are for this purpose dimensioned in such manner that the fresh air quantities flowing out through said openings correspond as closely as possible to the values of evaporation given to the right of the diagram in Fig. 3. In this manner it becomes possible to supply to the different portions of the drying section the exact heat quantities required for superheating the vapor, and thus, with the least possible supply of heat to attain the highest efliciency possible and consequently also the highest capacity possible. If a floor 27 is not used, the apertures 24 in the tubes 25 may instead be dimensioned in such manner that the fresh air quantities flowing out at the different pointscorrespond to the above-mentioned di erent quantities of evaporation.

The temperature of the heated freshair which is supplied from the passage 23 below the drying section shall be so high, and the quantity of the said fresh air shall'be so large that the heat contained in the same is suflia cient for superheating the entire quantity of vapor-in the moist air escaping from the drying section, so that precipitation of water from said air is securely prevented. Thus, if

the quantity of the fresh air let out belowthe drying'section is decreased its temperature must be increased, and vice versa. In order to attaln a good heat economy it is of course also desirable that the fresh air to be,

which is to be admitted into the machine room in order to effect the required ventilation and V cooling of the same.

Fig. 2 shows a slightly modified construcfresh air below the drying section, said construction being adapted to be used in such cases when for some reason or other the side walls of the passage 23 can not suitably be made whole. The longitudinally extendingv pipes 38 which are connected to the fresh air supplying pipe 22,.are in this case located on or, if desired, in the bottom of the passage 23, and are connected at a plurality of points by means of vertical pipes 39 with twodistributing pipes 40 extending in the longitudinal direction'of the passage. Said pipes 40, which may suitably be placedapproximately on alevel with or slightly below the lustrated in the drawing are only to be regarded as examples of the invention, and it will be understood that the same may be furciple and scope of the invention.

eral ways without departing from the prin- I claim 1. The method of increasing the capacity of drying installations in which the heat res quired for the drying is supplied directly to the drier, which consists in supplying fresh air to the drying installation,heat1ng a portion of s'uchfresh air to a higher temperature than the remaining portion, admitting such 'more highly heated fresh air adjacent the drier and causing it to flow along the sides of the drier and to mix withmoist air escaping from the drier, and admitting the fresh air heated to the lower temperature into the room in which thedrier is placed at a greater distance from said drier, for the purpose a f ventilatin and cooling the room.

2. T l ie method of increasing the capacity of drying installations in which the heat required for the drying is supplied directly to the drier, which consists in supplying fresh air to the dryin installation, heating a portion of such fresh air toa higher temperature than the remaining portion, admitting such more highly heated fresh air adjacent the drier and causing it to flow along the sides heated to the lower temperature into the room.

of the drier and to mix with moist air escaping from the drier, admitting the fresh air in which the drier is placed at a greater dis-- tance from said drier, for the purpose of ventilating and cooling the room, and utiliz-.

ing hot and moist waste air from the drier for heating the fresh air by conducting such waste air through at least two heat exchangers arranged in succession through which the fresh air is conducted in such manner that a portion of the same is thereby heated to a higher temperature than the other portion. I

3. The method of increasing the capacity of drying installations in which the heat required for the drying is supplied directly to the drier, which consists in supplying fresh air to the dryin r installation, heating a portion of such fres 1 air to a higher temperature than the remaining portion, exhausting such more highly heated fresh air below the drier and causing it to flow upwards along the sides of the drier and to mix with moist air escaping from the drier, and admitting the fresh air heated to the lower temperature into' the room in which the-drier is placed at a greater distance from said drier, for the purpose of ventilating and cooling the room.

4. The method of increasing the capacity of drying installations in which the heat required for the drying is supplied directly to the drier, whichconsists in supplying fresh air to the drying installation, heating a portion of such fresh air to a higher temperature than the remaining portion, exhausting such more highly heated fresh air below the drier and causing it to flow upwards along the sides of the drier and also through the drier and to mix with moist air escaping from the drier, and admitting the fresh air heated to the lower temperature into the room in which the drier is placed at a grcaterdistance from said drier, for the purpose of ventilating and cooling the room.

5. The method of increasing the capacity of drying installations in which the heat required for the drying is supplied directlyto the drier, and in which the evaporation of water is different from different portions of the drier, which consists in supplying fresh air to the drying installatioiuheating a portion of such fresh air to a higher temperature than the remaining portion, admitting such more highly heated fresh air adjacent the drier and causing it to flow along the sides of ventilating and cooling the room.

6. The method of increasing the capacity of drying installations in which the heat required for the drying is supplied directly to the .drier, and in which the evaporation of water is different from different portions of the drier, which consists in supplying fresh air to the drying installation, heating a. portion of such fresh air to a higher temperature than the remainingportion, exhausting suchmore highly heated fresh air below the drier and causing it to flow upwards along the sides of the drier and to 'mix with moist air escaping from the drier, regulating the admission of such more highly heat-ed fresh air in such manner that thequantities of fresh air admitted to different portions of the drier lUU room in which the drier is placed at a greater distance from said drier, for the purpose of ventilating and cooling the room. a

7. The combination with a drying installation in whic the heat required for the drying is supplied directly to the drier, of means for increasing the capacity of the installation, said means comprising two heat exchanges located above the drier and connected to one another, means for drawing hot and moist waste air from the drier through said heat exchangers in succession, means for conducting fresh air through saidheat exchangers, a

passage extending below the drier and adaptis supplied directly to for increasing the'capacity ofthe installa ed to admit heated air to the drier, a conduit connecting said passage to the fresh air outlet. of the heat exchanger through which the hot waste air from the drier passes first, and a bond-nit leading from the fresh air outlet of the heat exchanger through which the hot waste air from the drier passes last to the-room in which the drier is placed in such manner as to admit heated fresh air fromsaid lastmentioned heat exchanger into said room at a distance from the drier. v

8. The combination with a drying installation in which the heat required for the drying is supplied directly to the drier, of means for increasing the capacity of the installation, said means comprising two heat exchangers located above the drier and connected to one another, means for drawing hot and moist waste air from the drier through said heat exchangers in succession, means for conducting fresh air through said heat exchangers, a passage extending below the drier and adapted to admit heated air to the drier, a conduit connecting said passage to the fresh air outlet of the heat exchanger through which the hot waste air from the drier passes first, a conduit leading from the fresh air outlet of the heat exchanger through which the hot waste air from the drier passes last to the room in which the drier is placed in such manner as to admit heated fresh air from said last-mentioned heat exchanger into said room at a distance from the drier, a conduit connecting the fresh air outlet of the heat exchanger through which the waste air from the drier passes last with the fresh air inlet ofthe heat exchanger through which the waste air passes first, and an adjustable damper in said conduit.

9. The combination with a drying installation in which the heat required for the drying the drier, of means tion, said means comprising two heat exchangers located above the drier and connected to one another, means for drawing hot and moist Waste air from the drier through said heat exchangers in succession, means for conducting fresh air through said heat exchangers, a passage extending below the drier and adapted to admit'heated air to the drier,

a floor covering said passage, said floor being.

provided with a plurality of openings of Varying dimensions substantially corresponding to the quantities of water evaporated from the various portions of the drier located above such openings, a conduit connecting said pasthe drier is placed in such manner as to admit heated fresh air from said last mentioned heat exchanger into said room at a distance from the drier. 1

10. The combination with a dryinginstallation in which the heat required for the drying is supplied directly to the drier, of means for increasing the capacity .of the installation, said means comprising two heat exchangers located above the drier and connected to one another, means for drawing hot and moist waste air from the drier through said heat exchangers in succession, means for conducting fresh air through said heat exchangers, a passage extending below the drier and adapted to admit heated air to the drier, dis-c tributing'pipes provided in said passage, said pipes being provided with a plurality of apertures of varying dimensions substantially correspondingto the eguantities of water evaporated from the various portions of the drier located above such apertures, a conduit connecting said distributing pipes to the fresh air outlet of the heat exchanger. through which the hot waste air from the drier passes first, and a conduit leading from thefresh air outlet of the heat exchanger through which the hot waste air from the drier passes last to the room in which the drier is placed in such manner as to admit heated fresh air from said last-mentioned heat exchanger into said room at a distance from the drier.

JOHAN GUSTAF OLSSON. 

